Alexion Waits To Hear From FDA On Drug Candidate

Cheshire-based Alexion Pharmaceuticals has completed its submission for federal approval of a drug to treat soft bone disease, a genetic form of rickets that varies greatly in its severity.

Alexion's biological drug candidate, asfotase alfa, is an enzyme replacement therapy, designed to treat hypophosphatasia (HPP). It's estimated that one in 100,000 births is an infant with the severe variant of the disease. Some children are stillborn because the HPP was so severe, no skeleton formed at all.

For those whose symptoms show up in early infancy, only 27 percent live past age 5.

In Alexion's clinical study of asfotase alfa, 33 of 37 of patients whose symptoms began before age 6 months and who were treated with asfotase alfa survived five years. That comes out to 89 percent.

Alexion also tested children with less severe HPP, and their pain and weakness greatly decreased on the experimental drug.

Some people with mild forms of HPP may have no bone problems at all, according to the Soft Bones Foundation. Milder forms of HPP can also cause cavities and tooth loss.

Soft Bone disease is different from brittle bone disease, which is estimated to affect 20,000 to 50,000 people in the United States.

Alexion has not heard back from the Food and Drug Administration since its submission Dec. 30, but typically, the agency aims to approve or deny drug candidates within 10 months.

If approved, asfotase alfa would become Alexion's second drug on the market. Soliris, which also treats ultra-rare diseases, brought $1.6 billion in revenue to the company in the first nine months of 2014. The drug costs more than $400,000 a year and is the most expensive drug on the market in the United States.